Haven't pulled an air pump, so I can't say much about elect. hook-ups.
Regarding the belt. I'll assume you have a serpentine belt. Not sure if yours is the M103 or M104 motor. I believe the belt issue is very similar either way.
You'll need 2 special tools. Some here have gotten by with just one or possibly none.
The first tool is a Stahl-Wille 6-point-8mm allen type socket that is used to loosen the bolt in the center of your viscouos fan assembly. The second is a ft. long steel rod that's inserted in a U-shaped area on the engine behind the fan hub. There's a small bend in the rod that rests in this U-shaped groove and from there, it's inserted into a hole in tha back of the fan hub. This locks the fan so you can then loosen the bolt in the front of the fan assembly.
You may be able to buy these 2 tools at this sites parts facility. If not, try:
They carry specialty tools for MBs. Their phone number is 800-243-1220. There are MB parts specialists at this number who will know what I've described.
You need to remove the fan in order to get the serp. belt off. Some here may say they've taken them off without pulling the fan. I've had mine off many times and have yet to surmise how that was ever done with the fan remaining on?
I'd suggest that you obtain some doc on all of this. The CD-Rom is good, or you may try to find a hard copy M103 engine manual from: